Trump’s advance towards Cleveland has been marred by violence. One protestor at a Trump rally in Tucson, Arizona was beaten by Trump supporters while being escorted out of the rally. Another white Trump supporter assaulted an African American protestor at a Trump event in North Carolina. This same man was later recorded as saying that if he ever saw the protestor again, “we may have to kill him”. A Trump rally scheduled to take place in Chicago was cancelled due to worries that violence might break out between Trump supporters and anti-Trump protestors. And it did. Nor are these isolated incidents, Trump supporters have punched and kicked their way through nearly every campaign stop along the way.

The Project on Explaining and Mitigating Electoral Violence seeks to utilize techniques at the forefront of political science research to understand the causes of electoral violence worldwide, and to develop forecasting techniques that will allow researchers to predict which elections may turn violent. Yet, when we began out project, we did not consider that we would have to consider the United States election of 2016 a possible case study in electoral violence.

The Trump campaign, with its fervent supporters, is the only campaign where violence has come to be expected at rallies and speeches, if not outright encouraged by the candidate himself. While the ongoing violence has turned many voters away from the Trump campaign, both Republican and Democrat, the controversy surrounding violence at Trump rallies has done little to hurt his support among the section of the American electorate that has embraced Trump. According to a CBS/New York Times poll, 8 in 10 Trump supporters agree with Trump’s calls to treat protestors violently.

Elections in the United States rarely display the levels of incivility that has currently drawn international attention to the Trump campaign. America has seen its share of electoral violence. Erica Chenoweth has pointed out that electoral violence was routine up until the turn of the twentieth century. Violence erupted again in Chicago in 1968. Yet not since then have presidential election cycles been marred by violence. Pundits and politicians alike have been stunned by the outbreaks of violence that have occurred at Trump campaign events, but perhaps academic research into the causes of violence and conflict – especially electoral violence – can help formulate an answer.

Our project’s cross-national focus, along with insights from over a decade of research into the causes of various types of violence around the world can help shed some light on why this kind of violence seems to be growing more common among Americans who strongly support Donald Trump’s candidacy for president. Across multiple studies employing cross-national regression models to explain the causes of electoral violence, the most common variables correlated with electoral violence were a low level of national wealth, large populations, past outbreaks of electoral violence, and a country’s level of democracy.

Thanks to research conducted into the correlates of support for Donald Trump, we know that voters who tend to favor Trump have similar socio-economic profiles to citizens of countries that are more prone to experiencing electoral violence. Countries where outbreaks of electoral violence are common tend to be poor, to have large, economically disadvantaged populations, to have previous histories of violence, and they tend to be less democratic. Voters who support Donald Trump tend to be economically disadvantaged, with lower levels of education, and thus less opportunity to hold down well-paying jobs, or with “blue collar” manufacturing jobs (an economic sector on the decline in America), have a history of voting for previous segregationist or populist candidates like George Wallace and less history of voting for liberal or moderate Republicans, and tend to score high on tests for authoritarian personality traits.

Since 2008, America has also seen an unprecedented rise in the number of extremist organizations, including hate groups affiliated with white supremacist movements, though membership in organized extremist groups declined in 2014 and 2015. According to research conducted by the Southern Poverty Law Center (SPLC), the rise in membership in these hate groups is closely tied to deteriorating economic conditions faced by many poor whites, rising Latino immigration, and the election of America’s first mixed-race president. Viewed in the context of the literature on the correlates of cross-national political violence, this is unsurprising. We know that declines in economic growth, influxes of individuals with different ethnic identifications, and lack of economic opportunity tend to drive similar patterns of violence in diverse areas of the globe. And while these groups appear to be waning in number, the SPLC and other organizations warn that this decline in hate may be deceptive as the racist, xenophobic, and nationalist message of extremist organizations has now moved into the mainstream of American politics.

Could the fact that the message of these violent extremist groups is now given national prominence by Donald Trump, the leading candidate for the Republican Party, be fuelling the violence at his rallies? We know that Trump’s supporters tend to have similar demographic profiles to individuals who may belong to extremist organizations, or at least find the message of these organizations appealing. We also have some ideas why these individuals identify with the violent message of hate groups and Donald Trump. Trump’s message, and the message of hate groups, resonates among a segment of the American electorate that sees its economic position as precarious, and threatened by immigration. The grievances among this section of the American electorate – imagined or real – have indeed led to violent incidents. Two men in Boston beat a homeless man, and their reason for doing so was that the man appeared to be Hispanic. The man arrested for the assault was quoted as saying “Donald Trump was right, all these illegals need to be deported”.

We know from academic research that grievances are often a powerful cause of political violence. While all of the above analysis is speculative, it at least makes some intuitive sense. Trump has given disaffected whites an opportunity to violently express their dissatisfaction with their political and economic powerlessness by providing the racist and xenophobic message of many fringe organizations with a mainstream mouthpiece. His failure to punish those of his supporters who do engage in violence has given them a sense that such violence is permissible. This is not to suggest that all Trump supporters are card-carrying members of the KKK, but to suggest instead that Trump’s campaign messages of building a wall along the Mexican border, deporting Latino/a immigrants, engaging in trade wars with China, and not allowing the immigration of Muslims to America have activated latent racial attitudes which once seemed taboo, but now appear to be acceptable opinions to hold, at least at Trump rallies. The Republican Party is quickly realizing that this genie cannot be put back into the lamp so easily.

Fortunately, there is an easy solution to quell this violence, though it appears unlikely to be implemented. As he is the candidate who, by triggering feelings of grievance among his supporters, incites people to violence, Donald Trump and his supporters bear the responsibility of the electoral violence his campaign has wrought. Trump should immediately and forcefully denounce the use of violence at his campaign events, and lower the tone of nationalist, nativist, and populist rhetoric at this rallies. His supporters should likewise remember that the democratic process cannot be subverted by force, and that every American has a voice and a right to express their political opinions. Rather than making America great again, Donald Trump is bringing out the worst in his supporters. He may very well have legitimate points to make in the political arena, but he should make them in a way compliant with the norms of traditional campaign behavior. Unfortunately, he has shown little willingness to do so, and is unlikely to adopt a more moderate tone in the future. This is not making America great. America serves as a model for how other countries can peacefully discuss divisive political issues by conducting its elections peacefully. Given Trump’s actions, despots around the world will have little incentive to comport themselves in a peaceful manner if Trump should be the nominee.

David Muchlinski is a postdoctoral research associate with the project “Explaining and Mitigating Electoral Violence” at the University of Glasgow. His research interests include dynamics of political violence, electoral politics, machine learning, and forecasting. You can follow him on Twitter at @DMuchlinski.